At a seminar organised by the British Property Federation (BPF) Clark reiterated his commitment to overhauling the planning system. There is "too little planning in this country, not too much," he said.

The minister, who joined a panel which included Adam Marshall of the British Chambers of Commerce and Dame Fiona Reynolds, director general of the National Trust, sought to reassure critics that the much-debated presumption in favour of sustainable development was not a loophole for builders. He said the government had no intention of changing the purpose of the planning system.

His speech focused on the "distillation" of 1,300 pages of current planning regulation into just 52 contained in the NPPF. Clark admitted it had been a difficult task and that some changes had been lost in translation.

Reynolds, who said she had been "horrified" by the draft paper, claimed the NPPF was not a balanced document and "should not be used as a tool to promote the economy". She highlighted concerns about the definition of sustainable development, as well as the use of brownfield sites and the risk of urban sprawl.

Speaking to the Guardian Local Government Network, Clark explained that the NPPF seeks to apply the Brundtland definition of sustainability, "development that meets the needs of the present without compromising the ability of future generations to meet their own needs".

He said: "We've got a definition in the draft and I have said that we'll listen to responses to the consultation. We've used the definition that previous governments have used but people have suggested that it could be clearer there, so we will respond to that."

The minister was pressed on the removal of the term "brownfield" from the draft document. "It was never my intention to depart from the obviously desirable situation in which derelict land should be brought back into use," he said.

His admission may go some way to reassuring opponents of the reforms who claim that the document paves the way for unchecked development on greenbelt land across the country.

The panel also commented on the role of planning officers, who Reynolds and Clark agreed were undervalued and overworked. Both stressed the need for more support for officers, who Clark said were often caught in the middle of difficult planning disputes.

The NPPF is under consultation and CLG welcome responses to it. The consultation will end on 17 October